RU2697864C2 - Method and kit for determining iron ion dosage in lubricating compositions - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: disclosed is a method of determining iron ions in lubricating compositions, involving the following steps: a) sampling the analyzed lubricating composition into a first container; b) placing said first container containing the analyzed sample on the magnet; c) adding to the second container: a first aqueous reactive composition (CR1) containing at least one extractant of trivalent iron ions and divalent iron from the oil phase into the aqueous phase; a second aqueous reactive composition (CR2) containing at least one ferric ion (Fe³⁺) to obtain divalent iron ions (Fe²⁺); a third reactive composition (CR3) containing at least one substance destabilizing the emulsion; and a fourth reactive composition (CR4) in an aqueous solution containing a complexing agent of divalent iron ions, characterized by a discolouration during complexation with divalent iron ions; and mixing thereof; d) performing photochemical measurement of optical density of mixture obtained at step c); e) collecting a plurality of drops of the lubricating composition contained in the first container held in a position on the magnet and adding said several drops to a second container containing a mixture of first, second, third and fourth reactive compositions obtained at step c); f) mixing the mixture obtained at step e); g) performing photochemical measurement of optical density of mixture obtained at step f). Also disclosed is a kit for implementing the above method.

EFFECT: determination of iron ions, trivalent iron ions and ferrous iron, obtained as a result of corrosion of metal parts in the engine – in lubricating compositions, which are extracted during use under engine cylinders.

22 cl, 2 dwg, 1 tbl, 1 ex

Description

The present invention relates to a method for determining corrosive iron, that is, ferric ions and ferrous iron, in lubricating compositions that are in use, more specifically, in lubricating compositions of engines in use, more specifically, marine engines . This application also relates to a kit for implementing this method.

Engines, and in particular marine engines, are subjected to significant stresses during operation, in particular frictional stresses, and are exposed to corrosion, in particular marine engines, for example, due to the presence of sulfur in the fuel, which is converted to sulfuric acid during combustion . To reduce these stresses, lubricating compositions are generally used.

Due to the presence of these phenomena, in particular friction and corrosion, metal particles or contaminants, in particular iron particles, ferric ions and ferrous ions, are released into these lubricating compositions. These metallic contaminants, if present in an excessively large amount, can lead to a change in the properties of the aforementioned lubricating compositions, and thus their performance characteristics become harmful to the engine (in particular, resulting in a shortened service life). Therefore, it is advantageous to determine these metallic contaminants in lubricating compositions in order to determine the decomposition state of these compositions and, thereby, the optimum oil change time.

In addition, the analysis of these metallic pollutants also makes it possible to determine the extent to which these phenomena occur, in particular friction and corrosion, and make decisions regarding the maintenance and protection of lubricated equipment, in particular by adjusting the amount of lubricant composition added.

Some laboratories have suggested analyzing samples of lubricant compositions used to determine the amount of metal contaminants. However, in this case, sending samples, a long analysis time and, therefore, delayed adoption of measures are required.

Therefore, it would be advantageous to propose a method for the analysis of iron, in particular, ferric ions and ferrous iron, resulting from corrosion in the lubricating compositions used, as well as a kit adapted to implement this method, which can be used "in place" and is fast and reliable.

There are colorimetric analyzes, using which visually determine the range of concentration of iron as a result of comparison with reference samples. However, these methods are rarely reliable.

A method for analyzing the amount of iron contained in a lubricating composition in use is also known from WO2006127098. However, when using this method, it is precisely the total iron contained in the said lubricating composition that is determined, that is, both dispersed iron produced as a result of the presence of friction phenomena and ferric and ferrous iron ions produced as a result of corrosion. Therefore, when using this method, it is impossible to determine the actual impact of each of these two phenomena taken separately, and it is impossible for the operators to take appropriate measures.

Therefore, one of the objectives of the present invention is to provide an in-place analysis method for determining iron ions, ferric ions and ferrous ions — produced, in particular, as a result of corrosion of metal parts in an engine — in lubricating compositions that are recovered during use, in particular under the engine cylinders.

Another objective of the present invention is to propose the aforementioned method, where obtaining a sample for analysis is quick and easy.

One additional objective of the present invention is to propose the aforementioned method, which is quick to implement, preferably requiring less than 10 minutes to complete, which is reliable and reproducible.

One additional objective of the present invention is to propose a method to achieve measurement errors within somewhere around 10 ppm. and allowing measurements in the range from 0 to 900 ppm

One additional objective of the present invention is to provide a kit that makes it possible to implement the aforementioned method, which is quick and easy to use.

After reading the following description of the invention, other objectives will become apparent.

All these goals are achieved in the present invention, which provides a method of determining "in place" for iron ions, in particular, ferric ions and ferrous iron, in lubricating compositions and in lubricating compositions in use, in particular, for example, extracted at the bottom engine cylinders, using photochemical measurements after the reaction between iron ions and the complexing agent of iron ions, the complexation reaction causes a color change, which can be Qualitatively characterized using spectrophotometry.

The method of the invention for determining iron ions, in particular ferric and ferrous ions, in lubricating compositions comprises the following steps:

a) sampling the analyzed lubricating composition, for example, at the bottom of the engine cylinders, in the first container;

b) the location of the first container containing the sample to be analyzed on a magnet;

c) adding to the second container:

○ the first aqueous reactive composition CR1 containing at least one extractant of ferric ions and ferrous iron from the oil phase to the aqueous phase;

○ a second aqueous reactive composition CR2 containing at least one ferric ion reducing agent (Fe ^{3 +} ) to produce ferrous ions (Fe ^{2 +} );

○ a third reactive composition CR3 containing at least one emulsion destabilizer; and

○ the fourth reactive composition CR4 in an aqueous solution containing a complexing agent of ferrous ions, characterized in that the substance changes color when complexed with ferrous ions;

and mixing;

d) optional photochemical measurement of the optical density of the mixture obtained in stage c);

f) selecting a few drops of the lubricating composition contained in the first container, held in position on the magnet, and adding these few drops to a second container containing a mixture of the first, second, third and fourth reactive compositions obtained in stage c);

f) mixing the mixture obtained in step e);

g) conducting a photochemical measurement of the optical density of the mixture obtained in step f);

h) determining the amount of ferrous ions in the lubricating composition based on the measurement results obtained in stages d) and g).

Based on stage a), it is necessary to understand that it is the selected sample that is placed in the first container.

The lubricating composition to be analyzed is preferably an engine lubricant composition, preferably a marine engine lubricant, for example, a marine engine or a hydroelectric engine, and the like. Preferably, the lubricating composition is a lubricating composition for a 2 stroke marine engine. Preferably, the analyzed lubricating composition is a used lubricating composition collected at the bottom of the engine cylinders.

The lubricating composition contemplated by the present invention comprises at least one lubricating base oil. In general, lubricating base oils may be mineral, synthetic, or vegetable oils and mixtures thereof. In general, the mineral or synthetic oils used are assigned to groups I to V of the classification defined by the API Institute (or their equivalents in the ATIEL classification) in the manner described below. Classification is determined by the API in the publication: American Petroleum Institute 1509 «Engine oil Licensing and Certification System» 17 ^th Edition, September 2012. ATIEL Classification is determined by the publication: «The ATIEL Code of Practice» , Number 18, November 2012.

Saturated Compounds Sulfur level Viscosity index Mineral oils from group I <90% > 0.03% 80 ≤ IW <120 Hydrocracked oils from group II ≥ 90% ≤ 0.03% 80 ≤ IW <120 Hydrocracked and hydroisomerized oils from group III ≥ 90% ≤ 0.03% ≥ 120 Group IV PAO (poly-alpha olefins) Group V Esters and other bases not included in the bases of groups I to IV

Mineral oils from group I can be obtained by distillation of selected naphthenic or paraffinic crude oils followed by purification of the obtained distillates using methods such as solvent extraction, solvent or catalytic dewaxing, hydroprocessing or hydrogenation. Oils from groups II and III are obtained using more complicated refining methods, for example, a combination of treatments selected from hydroprocessing, hydrocracking, hydrogenation and catalytic dewaxing. Examples of synthetic base oils from Groups IV and V include polyisobutenes, alkylbenzenes and poly-alpha olefins, such as polybutenes or esters.

In lubricating compositions, lubricating base oils may be used individually or as a mixture. For example, mineral oil may be combined with synthetic oil.

Cylinder oils for two-stroke marine engines are generally characterized by a viscosity class in the range from SAE-40 to SAE-60, in general SAE-50, which is equivalent to the kinematic viscosity at 100 ° C in the range from 16.3 to 21.9 mm ² / sec as measured in accordance with ASTM D445. SAE-40 class oils are characterized by kinematic viscosity at 100 ° C in the range from 12.5 to 16.3 cSt as measured in accordance with ASTM D445. SAE-50 class oils are characterized by kinematic viscosity at 100 ° C in the range from 16.3 to 21.9 cSt as measured in accordance with ASTM D445. SAE-60 class oils are characterized by kinematic viscosity at 100 ° C in the range from 21.9 to 26.1 cSt as measured in accordance with ASTM D445. The lubricating compositions of the invention are preferably characterized by kinematic viscosity as measured in accordance with ASTM D445 at 100 ° C. in the range from 12.5 to 26.1 cSt, preferably from 16.3 to 21.9 cSt. To obtain such a viscosity, the lubricating compositions of the invention may also contain one or more additives. Typically, a typical formulation for marine engines, preferably two-stroke, corresponds to classes ranging from SAE-40 to SAE-60, preferably SAE-50, (according to SAE J300 classification) and contains at least 40% (w / w) lubricating base oil of mineral or synthetic origin or mixtures thereof, adapted for use in a marine engine. For example, a group I lubricating base oil that meets the API classification may be used to formulate a cylinder lubricant. Lubricating base oils from group I are characterized by a viscosity index (VI) in the range from 80 to 120; their sulfur content is greater than 0.03%, and their saturated hydrocarbon content is less than 90%.

The lubricating composition of the invention may also contain an additive selected from among overbased detergents or neutral detergents. Detergents (detergents) are usually anionic compounds containing a long lipophilic hydrocarbon chain and a hydrophilic head, the associated metal cation is usually a metal cation of an alkali or alkaline earth metal. Detergents are preferably selected from among alkali or alkaline earth metal salts (in particular, preferably calcium, magnesium, sodium or barium) for carboxylic acids, sulfonates, salicylates, naphthenates and phenol salts. These metal salts may contain metal in approximately stoichiometric amounts relative to the anionic group (s) of the detergent. In this case, the term used is unsubstantial or “neutral” detergent additives, even though they also make some contribution to basicity. These “neutral” detergents are usually characterized by an RN (base number) value, as measured in accordance with ASTM D2896, less than 150 mg KOH / g or less than 100 mg KOH / g or even less than 80 mg KOH / g detergent additives. This type of so-called neutral detergent additive may partly contribute to the value of the HF lubricating compositions. Appropriate detergents used are, for example, neutral detergents related to the type of carboxylates, sulfonates, salicylates, phenolates, naphthenates of alkali and alkaline earth metals, for example, calcium, sodium, magnesium, barium. If the metal is present in excess (in an amount greater than the stoichiometric amount with respect to the anionic group (s) of the detergent additive), they will deal with the so-called superbase detergent additives. They are characterized by a high RH value greater than 150 mg KOH / g detergent, usually in the range from 200 to 700 mg KOH / g detergent, preferably from 250 to 450 mg KOH / g detergent. The excess metal, which gives the superbasic nature to the detergent additive, is in the form of oil-insoluble metal salts, for example, carbonate, hydroxide, oxalate, acetate, glutaminate, preferably carbonate. In the same superbasic detergent additive, the metals of these insoluble salts may or may not be the same as the corresponding metals in the oil-soluble detergent additives. They are preferably selected from among calcium, magnesium, sodium or barium. Therefore, superbasic detergents are in the form of micelles formed from insoluble metal salts, kept in suspension in a lubricating composition using detergents in the form of oil-soluble metal salts. These micelles may contain one or more types of insoluble metal salts stabilized by using one or more types of detergent. Overbased detergents containing one type of metal salt of a soluble detergent are generally designated according to the type of hydrophobic chain of this last detergent. Therefore, they are designated as belonging to the phenolate, salicylate, sulfonate, naphthenate type, depending on whether this detergent additive will be, respectively, phenolate, salicylate, sulfonate or naphthenate. Superbase detergents will be designated as mixed type in the case of micelles containing several types of detergents that differ from each other in the nature of their hydrophobic chain. The excess base detergent and the neutral detergent can be selected from among carboxylates, sulfonates, salicylates, naphthenates, phenolates and mixed detergents that associate at least two of these types of detergent. Oversubstrate detergent and neutral detergent, in particular, are compounds containing metals selected from among calcium, magnesium, sodium or barium, preferably calcium or magnesium. The overbased detergent additive may be overbased due to the presence of insoluble metal salts selected from the group of alkali and alkaline earth metal carbonates, preferably calcium carbonate. The lubricating composition may contain at least one superbase detergent and at least one neutral detergent, such as those corresponding to the above definition of the invention.

As mentioned in the foregoing discussion, in one embodiment of the invention, the lubricating composition is characterized by an OP value, as defined in accordance with ASTM D-2896, not greater than 50, preferably not more than 40, advantageously not more than 30, milligrams of potash when calculated per one gram of lubricating composition, in the range, in particular, from 10 to 30, preferably from 15 to 30, preferably from 15 to 25, milligrams of potash when calculated per one gram of lubricating composition. In this embodiment, it is possible that the lubricating composition does not contain detergents containing alkali or alkaline earth metals that are overbased due to the presence of metal salts of carbonic acid.

In yet another embodiment of the invention, the lubricating composition is characterized by a value of HF, as defined in accordance with ASTM D-2896 component of at least 50, preferably at least 60, more preferably at least 70, in the best case ranging from 70 to 100.

The lubricating composition may also contain at least one other additional additive selected from dispersing additives, antiwear additives or any other functional additives. Dispersing additives are well known additives used in the formulation of lubricating compositions, in particular for applications in the marine sector. Their main role is to retain in suspension particles that are present initially, or which appear in the lubricant throughout its use in the engine. They prevent agglomeration of particles as a result of the action of creating spatial difficulties. They may also exhibit a synergistic effect with respect to neutralization. Dispersing additives used as lubricant additives typically contain a polar group associated with a relatively long hydrocarbon chain, generally containing from 50 to 400 carbon atoms. The polar group usually contains at least one atom of an element of nitrogen, oxygen or phosphorus. Dispersing additives, which are especially used as lubricant additives, are compounds made from succinic acid. In particular, succinimides obtained by condensation of succinic anhydrides and amines, esters of succinic acid obtained by condensation of succinic anhydrides and alcohols or polyols find their use. Thereafter, these compounds can be processed using various compounds, in particular sulfur, oxygen, formaldehyde, carboxylic acids and compounds containing boron or zinc, to obtain borated succinimides, for example, or succinimides blocked by zinc. The compounds used as dispersants in lubricants also represent Mannich bases obtained by polycondensation of phenols substituted with alkyl groups, formaldehyde groups and primary or secondary amines. In one embodiment of the invention, the level of dispersant additive may be 0.1% or more, preferably in the range from 0.5 to 2%, preferably from 1 to 1.5%, (mass.) With respect to the total mass lubricating composition. Antiwear additives protect friction surfaces as a result of the formation of a protective film adsorbed on these surfaces. One most commonly used suitable additive is zinc dithiophosphate or DTPZn. Various phosphorus, sulfur, nitrogen, chlorine and boron compounds also fall into this category. There is a wide range of anti-wear additives, but the category most commonly used is the category of phosphosulfurized additives, such as metal alkyl thiophosphates, in particular zinc thiophosphates, and more specifically zinc dialkyldithiophosphates or DTPZn. Preferred compounds are described by the formula Zn ((SP (S) (OR ₁ ) (OR ₂ )) 2, where R ₁ and R ₂ are alkyl groups, preferably containing from 1 to 18 carbon atoms. The DTPZn compound is usually contained in amounts in the range about 0.1 to 2% (w / w) with respect to the total weight of the lubricating composition. Also, antiwear additives that are often used are aminophosphates, polysulfides, in particular sulfurized olefins. Antiwear agents are also commonly found in marine lubricating compositions. and anti-seize additives of the nitrogen or sulfur type, such as metal dithiocarbamates, in particular molybdenum dithiocarbamate. Glycerol esters are also anti-wear additives, for example, mono-, di- and trioleinates, monomalimonates, monomalimonates, and monomalimonates. In one embodiment, the level of antiwear additives is in the range from 0.01 to 6%, preferably from 0.1 to 4%, (w / w) with respect to the total weight of the lubricating composition.

Other functional additives can be selected from among thickening agents, anti-foaming additives to counteract the effect of detergent additives, while they may, for example, be polar polymers such as polymethylsiloxanes, polyacrylates, antioxidant and / or anticorrosive additives, for example Organometallic detergents or thiadiazoles. They are known to those skilled in the art. The mass level of the content of these additives in the General case is in the range from 0.1 to 5% (mass.) In relation to the total mass of the lubricating composition.

Advantageously, in the method of the present invention, step b) makes it possible to deposit dispersed iron on the bottom of the first container, which may be contained in the analyzed lubricating composition and result from friction of engine parts. In a particularly advantageous case, sampling in step e) is carried out for the supernatant, which makes it possible to conduct an analysis solely with respect to ferric and ferrous ions, and thereby determine exclusively the degree of manifestation of the corrosion phenomenon alone.

In the present invention, the term "iron ions" refers to ferric ions and ferrous ions.

Lubricating compositions are generally formed from lubricating oils and additives and are therefore viscous and colored. Therefore, it is not easy to colorimetrically determine iron ions directly in a lubricating composition. Therefore, the present invention proposes the placement of iron ions in the aqueous phase. Advantageously, the first reactive composition (CR1) of the method of the present invention in an aqueous solution contains at least one extractant of ferric ions and ferrous iron to extract them from the oil phase of the lubricating composition into the aqueous phase. The extractant makes it possible to transfer all the ferric and ferrous iron ions from the oil phase of the lubricating composition to the aqueous phase, while the presence of water is ensured, in particular, by the CR1 composition, in which complexation will occur when using the complexing agent and analysis. This extractant, in particular, is selected from among substances that solubilize ferric and ferrous iron ions, and which are immiscible with a lubricating composition. Among these extractants, in particular, acids can be mentioned, preferably acids having a pKa value ranging from -5 to + 5, in particular sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, individually or as a mixture. Preferably, the acid is characterized by a pKa value of −3.

Composition CR1 may also contain other components, in particular, additives that contribute to the preparation of the composition and, in an advantageous case, make it possible to increase the speed of analysis. Among these additives, mention may be made of co-solvents promoting the solubilization of compounds of the reactive composition CR1, for example, those of the alcohol type, for example ethanol, 1,4-butanediol, preferably ethanol.

In the second reactive composition CR2 of the present invention, a ferric ion reducing agent for producing ferrous ions is preferably selected from the following reducing agents: hydroquinone, hydroxylamine hydrochloride, hydrazine, dithionite, individually or as a mixture. When using a reducing agent, it is possible to obtain a solution containing exclusively iron ions in the form of one form (structural unit), and thereby obtain a more reliable and accurate determination result.

Composition CR2 may also contain buffer solutions, making it possible to maintain a substantially stable pH value, preferably in the range from 2 to 7, more preferably from 2 to 3. Among the buffer solutions may be mentioned basic or acid solutions or mixtures thereof, for example , solutions, in particular concentrated, preferably weak acid and its conjugate base, salts, for example, sodium salts, such as sodium acetate, or a mixture thereof. Preferably, the buffer solution is selected from sodium acetate and acid solutions, in particular acetic acid, solutions of glycine and hydrochloric acid, solutions of ethanoic acid and sodium ethanoate, or solutions of citric acid and sodium phosphate.

Preferably, the first reactive composition of the present invention contains from 1 to 10% (wt.) Extractant. Preferably, the second reactive composition of the present invention contains from 1 to 15% (wt.) Reducing agent.

In a particularly advantageous case, the first and second reactive compositions can be mixed into one aqueous reactive composition CR1 ′, which then contains at least one extractant of ferric ions and ferrous iron from the oil phase into the aqueous phase, while introducing into the presence of water its contribution, in particular, the composition CR1 ', and at least one reducing agent, reducing ions of ferric iron (Fe ^{3 +} ) to produce ions of ferrous iron (Fe ^{2 +} ). Preferably, the reactive composition CR1 ′ contains from 1 to 15% (wt.) Reducing agent and from 1 to 10% (wt.) Extractant. This reactive composition CR1 'may also contain other components, in particular, additives that facilitate the preparation of the composition and, in an advantageous case, make it possible to increase the speed of analysis. Among these additives, mention may be made of co-solvents promoting the solubilization of compounds of the reactive composition CR1 ′, for example, of the alcohol type, for example ethanol or 1,4-butanediol, preferably ethanol, and / or buffers, which make it possible to maintain essentially stable pH, preferably in the range from 2 to 7, more preferably from 2 to 3; among the buffer solutions may be mentioned basic or acid solutions or a mixture thereof, for example, solutions, in particular concentrated, weak acid and its conjugate base, salts, for example, sodium salts, such as sodium acetate, or a mixture thereof. Preferably, the buffer solution is selected from sodium acetate and acid solutions, in particular acetic acid, solutions of glycine and hydrochloric acid, solutions of ethanoic acid and sodium ethanoate, or solutions of citric acid and sodium phosphate.

Preferably, the reactive composition CR1 ’of the invention comprises ethanol or 1,4-butanediol (preferably ethanol), sulfuric acid, hydroxylamine hydrochloride and sodium acetate in solution in water.

The third reactive composition CR3 of the method of the invention contains at least one emulsion destabilizing substance. The first, second and fourth reactive compositions and the reactive composition CR1 ’are aqueous compositions. When mixed with a lubricating composition, these aqueous compositions may form an emulsion. Therefore, the third reactive composition advantageously makes possible the destruction of the resulting emulsion and, thereby, makes possible a better phase separation. Therefore, the third reactive composition of the method of the invention favorably facilitates and accelerates the transition of ferric ions and ferrous iron of the oil phase of the lubricating composition to the aqueous phase, the presence of which is provided by the first, second and fourth reactive compositions or reactive composition CR1 ’. Advantageously, the destabilizing substance is formed from a compound immiscible with water. The destabilizing substance of the invention is preferably selected from among primary or secondary alcohols (C4 to C10), individually or as a mixture. Preferably, the destabilizing substance of the invention is selected from isoamyl alcohol, octan-1-ol, octan-2-ol, 1-heptanol, 2-ethylhexanol, 2-ethylbutanol, individually or as a mixture, preferably isoamyl alcohol, octane-1-ol, octan-2-ol, individually or as a mixture, preferably isoamyl alcohol, 1-heptanol, 2-ethylhexanol, 2-ethylbutanol, individually or as a mixture, preferably isoamyl alcohol.

Preferably, the third reactive composition of the method of the present invention contains from 20 to 100% (mass.) Of the substance that destabilizes the emulsion.

The third reactive composition of the present invention may also contain additives, for example, in the case of an excessively high flash point of a destabilizing substance; the third reactive composition of the invention may contain co-solvents making it possible to reduce the flash point of the composition. Among these co-solvents, light petroleum distillates may be mentioned, preferably containing less than 2% aromatic compounds, such as hydrocarbons, for example, preferably C9 to C16, for example C9 to C16 n-alkane, C9 to C16 isoalkane, from C9 to C16 cyclic hydrocarbons.

The fourth reactive composition CR4 of the method of the present invention contains a complexing agent of ferrous ions. This complexing agent is selected from among substances that complex ferrous ions, and complexation for which causes a color change that can be detected by measuring the optical density of the resulting solution using a spectrophotometer. After that, the measured optical density can be correlated with the content of ferrous ions and, thus, iron ions in the analyzed sample in terms of ppm. Preferably, the complexing agent is selected from among ferrozin, feren, phenanthroline and its derivatives, for example, bathophenanthroline, bipyridine, thioglycolic acid, nitroso-P salt (sodium salt of 3-hydroxy-4-nitroso-2,7-naphthalenedisulfonic acid), potassium ferricyanide (potassium hexacyanoferrate (III)), 2,4,6-tripyridyl-sim-triazine (TPTZ). Preferably, the complexing agent is selected from TPTZ, potassium ferricyanide or a nitroso-P salt. Preferably, the complexing agent is a nitroso-P salt.

Preferably, the fourth reactive composition contains from 0.5 to 5% (mass.) Complexing agent. Preferably, the reactive composition contains 1% (mass.) Complexing agent.

The determination method of the present invention is a colorimetric analysis method in which the optical density of a solution obtained by complexation between a complexing agent and ferrous ions is measured using UV-visible spectrometry and a spectrophotometer, preferably an electronic spectrophotometer. Therefore, optical density measurements in steps d) and g) are carried out using a spectrophotometer, preferably an electronic spectrophotometer.

The measurement of optical density using spectrophotometry is based on the Baire-Lambert law. Incident light with intensity I0 passes through the analyzed aqueous solution, part of this light is absorbed by the solution, and the resulting intensity I is transmitted through the solution. After that, determine the optical density (A) of the solution using the following equation:

It is possible to correlate the optical density with the concentration of ferrous ions in solution using a calibration curve giving a straight line connecting the optical density with the concentration of ferrous ions in solution with a known concentration. An electronic spectrophotometer is previously calibrated using this calibration curve, and the measured optical density makes it possible to determine the amount of ferrous ions in ppm. in the analyzed sample.

In one first embodiment, a measurement for a blank optical density sample can be performed on a container containing a mixture of the four reactive compositions defined above. After that, this measurement result for a blank sample is considered as a reference for a spectrophotometer, and each of the measurement results for the compositions obtained in step f) is compared with this value for a blank sample, which leads to a true optical density value in accordance with the explanation of the invention presented below.

In one second embodiment, to obtain a reliable accurate value of the optical density and, thereby, indirectly the concentration of ferrous ions, a blank sample is obtained to take into account the magnitude of the effect of the second container and the first, second, third and fourth reactive compositions on the measurement result of optical density. To accomplish this, step d) is carried out to measure the optical density in relation to the mixture obtained in step c) in a second container. By using the difference between the optical density obtained in step g) and the optical density obtained in step c), the true optical density of the solution obtained in step f) can be obtained, and thus it is possible to determine the corresponding amount of iron ions. In a particularly advantageous case, an electronic spectrophotometer is programmed to calculate the difference between the optical densities measured in steps d) and g), and thereby the corresponding concentration of iron ions in the analyzed solution in ppm.

In step g), a second container is placed in the spectrophotometer so that the emitted incident light passes exclusively through the aqueous phase. As will be seen below, the spectrophotometer preferably provides an adapted compartment for receiving a sample, preferably at an adapted angle, so that the emitted incident light passes exclusively through the aqueous phase.

In a particularly advantageous case, all the data of stage d), g) and h) are carried out directly using an electronic spectrophotometer, which is programmed accordingly.

Preferably, the mixing in step f) is carried out by turning the container upside down at least 5 times, for example 10 times. After mixing, the container is placed directly in a spectrophotometer. Advantageously, mixing is light mixing.

Preferably, the measurement in step g) is carried out in less than 10 minutes after the container is placed in the spectrophotometer, preferably the measurement is carried out after 5 minutes after the container is located in the spectrophotometer, this time being the time required for the complexation reaction to take place between the complexing agent and the ferrous ions .

Preferably, each of the first, second, third, and fourth reactive compositions is added to a second container with a proportion in the range of 5 to 10 ml. Preferably, each of the first, second, third and fourth reactive compositions is added to the second container with a share of 5 ml.

Preferably, each of the third and fourth reactive compositions and CR1 ’compositions are added to a second container with a proportion in the range of 5 to 10 ml. Preferably, the third and fourth reactive compositions and the CR1 ’composition are added to the second container with a proportion of 5 ml.

In yet another embodiment, the first, second, and third reactive compositions may be contained in a single reactive CR composition that is previously prepared.

Preferably, in step e), 1 to 10 drops, preferably 3 drops, that is, approximately 0.075 g or 100 μl of the analyzed lubricating composition, are added to the second container.

The method of the present invention can be repeated as many times as there will be samples to be analyzed. In this case, there are as many first and second containers as there will be analyzed lubricating compositions. In a particularly advantageous case, during stage d), stages d) and g) should be carried out for each analyzed sample one after the other, and not according to the methodology for carrying out stages d) for each of the analyzed samples and after that stages g) for each of the analyzed samples ; The spectrophotometer is preferably effectively parameterized to compare each of the mixtures obtained after steps c) and f).

In a particularly advantageous case, the method of the present invention is reliable, it makes it possible to determine from 0 to 900 ppm. iron in the samples, preferably from 50 to 700 ppm

Advantageously, the method of the invention is quick and simple and does not require the operator to have special knowledge. Advantageously, when using the method of the invention, it is possible to obtain a result with respect to the amount of iron ions present in the lubricating composition in use after less than 10 minutes and with an error within about 10 ppm.

In a particularly advantageous case, the method of the present invention does not require heating of the analyzed samples or processing of dispersed iron.

The present invention also relates to a kit for implementing the method described above. This kit includes:

- the first aqueous reactive composition CR1, containing at least one extractant of ferric ions and ferrous iron from the oil phase of the lubricating composition into the aqueous phase;

- a second aqueous reactive composition CR2 containing at least one ferric ion reducing agent (Fe3 +) to produce ferrous ions (Fe2 +);

- a third reactive composition CR3 containing at least one substance that destabilizes the emulsion;

- the fourth reactive composition of CR4 in an aqueous solution containing a complexing agent of ferrous ions, characterized in that the substance changes color when complexed with ferrous ions;

- a spectrophotometer, preferably an electronic spectrophotometer;

- optionally at least one first container;

- at least one second container;

- optionally a D1 device for sampling the analyzed lubricating composition;

- a device D2 for receiving each of the first, second, third and fourth reactive compositions;

- a support having magnetic properties;

at least one D3 device for sampling several drops of the lubricating composition analyzed in step e).

Reactive compositions CR1, CR2, CR3 and CR4 are as defined above.

A spectrophotometer, preferably an electronic spectrophotometer, includes a light emitting device, for example, a light emitting diode; photoelectric sensor; a compartment for receiving a second container; optical density data processing software for conversion to ferrous ion concentration in ppm Preferably, the compartment for receiving the second container is located at a distance in the range from 10 to 50 mm, preferably from 15 to 30 mm, for example 24 mm, from the bottom of the second container and is oriented at an angle in the range from 35 to 75 °, preferably from 50 to 70 °, for example, 60 °, to ensure that the measurement of optical density exclusively in the aqueous phase of the mixture obtained in stage f) and containing a colored complex formed between the complexing agent and the ions of ferrous iron.

Preferably, the first container is made of plastic material or glass, preferably plastic material. It may not necessarily have a cork. Preferably, the kit includes at least as many first containers as there will be samples of the analyzed lubricating composition. Engines have from 4 to 14 cylinders, therefore at the same time there are at least 4 to 14 samples of the analyzed lubricant composition (one sample of the lubricant composition per one cylinder). Preferably there is at least one first container, preferably there is from one to 50 first containers, for example, from 5 to 40 first containers.

Preferably, the second container is an ampoule-shaped container provided with a stopper, preferably a test tube equipped with a stopper. It can be made of plastic material or glass, preferably glass. Preferably, the kit includes at least as many second containers as there will be samples of the analyzed lubricating compositions. Therefore, the kit includes from 1 to 100 second containers, for example, from 10 to 80 second containers, for example, 50 second containers.

The first and second containers may be containers made of glass or plastic; they may be disposable or suitable for cleaning. Preferably, in the invention, the first and second containers are disposable.

Preferably, the sampling device D1 of the analyzed lubricating composition is a syringe, preferably made of disposable plastic material. The kit may include as many D1 devices as there will be lubricant compositions to be analyzed, preferably the kit includes from 1 to 100 D1 devices, preferably from 10 to 80, for example 50.

Preferably, each of the devices D2 is a syringe, preferably made of disposable plastic material. A kit may include from 3 to 18 D2 devices, preferably from 3 to 6 D2 devices.

Preferably, the support having magnetic properties is a holder for receiving a first container containing an analyte lubricating composition and having a magnet in its lower part. Preferably, the support having magnetic properties is a stand comprising from 1 to 50, preferably 7, positions for receiving the first containers. Preferably, the support having magnetic properties consists of two parts, with the lower part including positions for receiving the first containers, each position including a magnet, and the upper part including positions for the second containers, the positions of the lower part and the positions of the upper part are preferably facing one to the other for quick and easy identification of analyzed lubricating compositions.

Preferably, the D3 device for collecting a few drops of the analyzed lubricant composition in step e) is a pipette, preferably made of disposable plastic material, or a direct displacement micropipette, for example 100 μl, for example of the Microman Gilson or Transferpettor type. There are at least as many D3 devices as there will be analyzed lubricant compositions. For example, a kit may include from 1 to 50 D3 devices, preferably 50 D3 devices.

In a particularly advantageous case, the kit of the invention can be folded into a box or box and therefore is easily transported.

FIG. 1 illustrates a kit of the invention.

FIG. 2 illustrates a magnetically supported support of the invention.

The kit in the figure (1) includes:

- a support 1 having magnetic properties, including positions 2, each of which has a magnet and is designed to receive the first containers 3, and positions 4, designed to receive the second containers 5;

- first containers 3;

- second containers 5;

- reactive composition 6 (CR1 ’);

- reactive composition 7 (CR3);

- reactive composition 8 (CR4);

- an electronic spectrophotometer 9, comprising a receiving compartment 10 for receiving second containers, preferably this receiving compartment forms an angle in the range from 35 to 75 °, preferably from 50 to 70 °, for example 60 °, with respect to the spectrophotometer body;

- at least one device 11 (D3); and

- at least three devices 12 (D2).

FIG. 2 illustrates a support 1 having magnetic properties, including positions 2, each of which has a magnet and is intended to receive the first containers 3, and positions 4, intended to receive the second containers 5.

The present invention will now be described with one non-limiting example of an embodiment of the method and kit of the invention.

Example

The operator puts the spectrophotometer in action.

a) The operator collects the analyzed lubricating compositions in the first containers 3 and places these containers in the magnet-including positions 2 of the support having magnetic properties, 1, after which any dispersed iron contained in the analyzed lubricating composition is attracted down to the bottom of the container located near the magnet.

b) After that, the operator uses three separate devices 12 (D2) to place each of the reactive compositions 6 (CR1 ’), 7 (CR3) and 8 (CR4) in as many second containers 5 as there will be analyzed oils. The contents of the second containers are mixed as a result of the inversion of the second containers 5. All of the second containers 5 are placed in positions 4 of the support having magnetic properties, 1.

c) After this, the operator places one of the second containers 5 in the sector for receiving 10 of the spectrophotometer 9 and measures the optical density of the solution contained in the second container 5.

d) This second container 5 is then placed back in one of the positions 4 of the support, which has magnetic properties, 1, and the operator using device 11 (D3) then adds three drops to it of one of the analyzed lubricating compositions contained in one of the first containers 3. To do this, the operator must be careful not to introduce the device to the bottom of the container 3 in order to avoid capture of any dispersed iron that may be present at the bottom of the container 3. After adding the lubricating composition In this case, the operator registers any color change resulting from the passage of the reaction between iron ions and the complexing agent of the reactive composition CR4.

e) Then the contents of the container 5 are mixed as a result of its inversion 10 times, after which it is placed in the sector for receiving 10 spectrophotometer 9.

f) The container 5 is left for 5 minutes in the sector for receiving 10 spectrophotometer 9 before measuring the optical density of the solution contained in the second container 5.

g) The spectrophotometer calculates the difference between the result of measuring the optical density when the container 5 contains only reactive compositions CR1 ’, CR3 and CR4 and the result of measuring the optical density when a lubricating composition is added to the container 5.

h) Based on the measurement result obtained in step g), the spectrophotometer determines the amount of iron ions contained in the analyzed lubricating composition.

After this, steps c) to h) are repeated for each of the analyzed lubricating compositions.

Claims (46)

1. The method of determining iron ions in lubricating compositions, comprising the following stages: a) sampling the analyzed lubricating composition in the first container; b) placing said first container containing the sample to be analyzed on a magnet; c) adding to the second container: a first aqueous reactive composition (CR1) containing at least one extractant of ferric ions and ferrous iron from the oil phase to the aqueous phase; a second aqueous reactive composition (CR2) containing at least one ferric ion reducing agent (Fe ^{3 +} ) to produce ferrous ions (Fe ^{2 +} ); a third reactive composition (CR3) containing at least one emulsion destabilizing substance; and a fourth reactive composition (CR4) in an aqueous solution containing a complexing agent of ferrous ions, characterized in that it changes color when complexed with ferrous ions; and mixing them; d) conducting a photochemical measurement of the optical density of the mixture obtained in step c); f) selecting a few drops of the lubricating composition contained in the first container, held in position on the magnet, and adding these few drops to the second container containing a mixture of the first, second, third and fourth reactive compositions obtained in stage c); f) mixing the mixture obtained in step e); g) conducting a photochemical measurement of the optical density of the mixture obtained in step f); h) determining the amount of ferrous ions in the lubricating composition based on the measurement results obtained in stages d) and g). 2. The method according to p. 1, where the extractant is selected from among substances solubilizing ferric and ferrous iron ions and immiscible with a lubricating composition. 3. The method according to p. 1 or 2, where the extractant is selected from sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid individually or as a mixture. 4. The method according to p. 3, where the extractant is sulfuric acid. 5. The method according to any one of paragraphs. 1 or 2, where a ferric ion reducing agent for producing ferrous ions is selected from hydroquinone, hydroxylamine hydrochloride, hydrazine, dithionite individually or as a mixture. 6. The method of claim 5, wherein the ferric ion reducing agent for producing ferrous ions is hydroxylamine hydrochloride. 7. The method according to any one of paragraphs. 1-6, where the destabilizing substance is selected from among primary or secondary alcohols (from C4 to C10), immiscible with water, individually or as a mixture. 8. The method according to claim 7, where the destabilizing substance is isoamyl alcohol, octan-1-ol, octan-2-ol, 1-heptanol, 2-ethylhexanol, 2-ethylbutanol. 9. The method according to any one of paragraphs. 1-8, where the complexing agent is selected from substances forming complex compounds with ferrous ions and for which complexation leads to a color change that can be detected by spectrophotometric measurement of the optical density of the resulting solution. 10. The method according to p. 1 or 2, where the complexing agent is selected from among ferrozin, feren, phenanthroline and its derivatives, bipyridine, thioglycolic acid, nitroso-P-salt (sodium salt of 3-hydroxy-4-nitroso-2,7-naphthalenedisulfonic acid), potassium ferricyanide (potassium hexacyanoferrate (III)), 2,4,6-tripyridyl-sim-triazine (TPTZ). 11. The method according to p. 9, where the complexing agent is a nitroso-P-salt. 12. The method according to any one of paragraphs. 1 or 2, where the first and second reactive compositions are included in the aqueous reactive composition CR1 ’. 13. A kit for implementing the method according to any one of paragraphs. 1 or 2, containing: - a first aqueous reactive composition (CR1) containing at least one extractant of ferric ions and ferrous iron from the oil phase of the lubricating composition into the aqueous phase; - a second aqueous reactive composition (CR2) containing at least one ferric ion reducing agent (Fe3 +) to produce ferrous ions (Fe2 +); a third reactive composition (CR3) containing at least one emulsion destabilizing substance; - a fourth reactive composition (CR4) in an aqueous solution containing a complexing agent of ferrous ions, characterized in that the complexing agent changes color when complexed with ferrous ions; - spectrophotometer; - at least one first container; - at least one second container; - at least one device (D1) for sampling the analyzed lubricating composition; - a device (D2) for receiving each of the first, second, third and fourth reactive compositions; - a support having magnetic properties; - at least one device (D3) for receiving a few drops of the lubricating composition analyzed in step e). 14. The kit according to p. 13, in which the extractant is selected from substances that solubilize ferric and ferrous iron ions and are immiscible with a lubricating composition. 15. The kit according to claim 13 or 14, wherein the extractant is selected from sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid individually or as a mixture. 16. A kit according to any one of paragraphs. 13-15, in which the reducing agent of ferric ions (Fe3 +) to ferrous ions (Fe2 +) is selected from hydroquinone, hydroxylamine hydrochloride, hydrazine, dithionite individually or as a mixture. 17. A kit according to any one of paragraphs. 13-15, in which the destabilizing substance is selected from primary or secondary alcohols (from C4 to C10), immiscible with water, individually or as a mixture. 18. The kit of claim 17, wherein the emulsion destabilizing agent is isoamyl alcohol, octan-1-ol, octan-2-ol, 1-heptanol, 2-ethylhexanol, 2-ethylbutanol. 19. A kit according to any one of paragraphs. 13-18, in which the complexing agent is selected from substances forming complex compounds with ferrous ions and for which complexation leads to a color change that can be detected by spectrophotometric measurement of the optical density of the resulting solution. 20. Set according to any one of paragraphs. 13-19, in which the complexing agent is selected from ferrosin, feren, phenanthroline and its derivatives, bipyridine, thioglycolic acid, nitroso-P-salt (sodium salt of 3-hydroxy-4-nitroso-2,7-naphthalenedisulfonic acid), potassium ferricyanide ( potassium hexacyanoferrate (III)), 2,4,6-tripyridyl-sim-triazine (TPTZ). 21. Set according to any one of paragraphs. 13-20, in which the first and second reactive compositions are included in the aqueous reactive composition CR1 ’. 22. A kit according to any one of paragraphs. 13-20, in which the spectrophotometer is an electronic spectrophotometer.

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